Introduction to Google Kubernetes Engine

We have used Kubernetes distribution K3s using Docker containers via k3d. In a production environment the burden of maintaining a Kubernetes cluster is often left to third parties. A managed Kubernetes as a service is often the best choice as the additional work required in maintenance exceeds the benefits of a personal cluster. In some, somewhat rare, cases setting up and maintaining your own cluster is a reasonable option. A case for it would be that your company/organization already has the hardware and/or wants to stay independent from providers, one such example could be a University. Another primary reason for operating your own Kubernetes cluster is that regulations rule out all other choices.

Maintaining your own Kubernetes cluster is one way to increase costs. The other is running servers that are not in use. To avoid costs Serverless solutions could be more cost-efficient. A Kubernetes cluster of improper size can get really expensive pretty fast. An excellent option to start out with would be a high-tier environment for serverless workloads, such as Google Cloud Run or AWS Fargate. In those you can run any container, compared to older solutions like Cloud Functions or AWS Lambda, which have wildly varying support for different languages, environments and tooling.

Let's focus on the Google Kubernetes Engine (GKE) costs for now. Note that the GKE costs a little bit more than its competitors.

The calculator here https://cloud.google.com/products/calculator offers us a picture of the pricing. I decided to try a cheap option: 5 nodes in 1 zonal cluster using 1 vCPU each. The datacenter location is in Finland and I don't need a persistent disk. If we wanted less than 5 nodes why would we even use Kubernetes? The total cost for this example was around 250 USD per month. Adding additional services such as a Load balancer increases the cost. If you find the billing for Google Cloud Platform confusing, you're not alone: Coursera has ~5 hour course for "Understanding Your Google Cloud Platform Costs".

During part 3 we will be using GKE either by using the free credits offered by Google. You are responsible for making sure that the credits last for the whole part and if all of them are consumed, I can not help you.

After redeeming the credits we can create a project with the billing account. The Google Cloud UI can be confusing. On the resources page we can create a new project and let's name it "dwk-gke" for the purposes of this course.

Install the Google Cloud SDK. Instructions here. After that login and set the previously created project to be used.

$ gcloud -v
  Google Cloud SDK 471.0.0
  bq 2.1.3
  core 2024.03.29
  gcloud-crc32c 1.0.0
  gsutil 5.27

$ gcloud auth login
  ...
  You are now logged in

$ gcloud config set project dwk-gke
  Updated property [core/project].

We can now create a cluster, with the command gcloud container clusters create. You can choose any zone you want from the list here. I chose Finland. Notice that one region (e.g. europe-north1) may have multiple regions (e.g. -a). Let's add another flag: --cluster-version=1.29. This will ask GKE to use a version that will be the default in April 2024. GKE release schedule can be seen here.

$ gcloud container clusters create dwk-cluster --zone=europe-north1-b --cluster-version=1.29 --disk-size=32 --num-nodes=3 --machine-type=e2-micro

ERROR: (gcloud.container.clusters.create) ResponseError: code=403, message=Kubernetes Engine API has not been used in project dwk-gke-xxxxxx before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/container.googleapis.com/overview?project=dwk-gke-xxxxxx then retry.

You can visit the link that was provided and enable the Kubernetes Engine API, just note that the url which is outputted is specific to your project name. Or, you can just execute the following command on the cli:

$ gcloud services enable container.googleapis.com
  Operation "operations/acf.p2-385245615727-2f855eed-e785-49ac-91da-896925a691ab" finished successfully.

$ gcloud container clusters create dwk-cluster --zone=europe-north1-b --cluster-version=1.29
  ...
  Creating cluster dwk-cluster in europe-north1-b...
  ...
  kubeconfig entry generated for dwk-cluster.
  NAME         LOCATION         MASTER_VERSION   MASTER_IP       MACHINE_TYPE  NODE_VERSION     NUM_NODES  STATUS
  dwk-cluster  europe-north1-b  1.29.8-gke.2200  35.228.176.118  e2-medium     1.29.8-gke.2200  3          RUNNING

If the command does not work, you need to install gke-gcloud-auth-plugin by following this.

It sets the kubeconfig to point in the right direction already. But if you need to do it again, we can set the kubeconfig like this:

$ gcloud container clusters get-credentials dwk-cluster --zone=europe-north1-b
  Fetching cluster endpoint and auth data.
  kubeconfig entry generated for dwk-cluster.

You can check the cluster info with kubectl cluster-info to verify it's pointing in the right direction.

Deploying to GKE

The cluster we have now is almost like the one we had locally. Let's apply this application that creates a random string and then serves an image based on that random string. This will create 6 replicas of the process "seedimage".

$ kubectl apply -f https://raw.githubusercontent.com/kubernetes-hy/material-example/e11a700350aede132b62d3b5fd63c05d6b976394/app6/manifests/deployment.yaml

Exposing the service is where the differences start. Instead of an Ingress we'll use LoadBalancer service. Now as a warning the next step is going to add into the cost of the cluster as well.

Apply the following:

service.yaml

apiVersion: v1
kind: Service
metadata:
  name: seedimage-svc
spec:
  type: LoadBalancer # This should be the only unfamiliar part
  selector:
    app: seedimage
  ports:
    - port: 80
      protocol: TCP
      targetPort: 3000

A load balancer service asks for Google services to provision us a load balancer. We can wait until the service gets an external IP:

$ kubectl get svc --watch
  NAME            TYPE           CLUSTER-IP      EXTERNAL-IP    PORT(S)        AGE
  kubernetes      ClusterIP      10.31.240.1     <none>         443/TCP        144m
  seedimage-svc   LoadBalancer   10.31.241.224   35.228.41.16   80:30215/TCP   94s

If we now access http://35.228.41.16 with our browser we'll see the application up and running. By refreshing the page we can also see that the load balancer sometimes offers us a different image. Note that this is available in port 80, so https will not work.

To avoid using up the credits delete the cluster whenever you do not need it

$ gcloud container clusters delete dwk-cluster --zone=europe-north1-b

And when resuming progress create the cluster back.

$ gcloud container clusters create dwk-cluster --zone=europe-north1-b --cluster-version=1.29

Closing the cluster will also remove everything you've deployed on the cluster. So if you decide to take a days long break during an exercise, you may have to redo it. Thankfully we are using a declarative approach so continuing progress will only require you to apply the yamls.

Persisting data in GKE

Google Kubernetes Engine will automatically provision a persistent disk for your PersistentVolumeClaim - just don't set the storage class. If you want you can read more about it here.

Deploy Ping-pong application into GKE.

In this exercise use a LoadBalancer service to expose the service.

If your Postgres logs say

initdb: error: directory "/var/lib/postgresql/data" exists but is not empty
It contains a lost+found directory, perhaps due to it being a mount point.
Using a mount point directly as the data directory is not recommended.
Create a subdirectory under the mount point.

you can add subPath configuration:

statefulset.yaml

# ...
volumeMounts:
- name: data
  mountPath: /var/lib/postgresql/data
  subPath: postgres
# ...

This will create a Postgres directory where the data will reside. subPaths also make it possible to use single volume for multiple purposes.

From Service to Ingress

Services are quite simple. Let's try using Ingress since it offers us additional tools in exchange for complexity.

NodePort type service is required with an Ingress in GKE. Even though it is NodePort, GKE does not expose it outside the cluster. Let's test this by continuing with the previous example.

service.yaml

apiVersion: v1
kind: Service
metadata:
  name: seedimage-svc
spec:
  type: NodePort
  selector:
    app: seedimage
  ports:
    - port: 80
      protocol: TCP
      targetPort: 3000

ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: seedimage-ing
spec:
  rules:
  - http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: seedimage-svc
            port:
              number: 80

When you have applied those you can view the port from the list of ingresses:

$ kubectl get ing
  NAME            CLASS    HOSTS   ADDRESS         PORTS   AGE
  seedimage-ing   <none>   *       34.120.61.234   80      2m13s

Now the address here will be the way to access the application. This will take a moment to deploy, responses may be 404 and 502 as it becomes available. The Ingress performs health checks by GET requesting / and expects an HTTP 200 response.

You have reached the end of this section! Continue to the next section:

2. Deployment Pipeline